This invention relates to work transporting feed dogs for sewing machines, and more particularly, to a novel work feed dog arrangement which may be converted readily to accommodate zig-zag or straight stitching.
For zig-zag sewing a throat plate with an elongated needle accommodating aperture as wide as the maximum zig-zag width is required and the side limbs of the work feed dog must be as widely spaced as the maximum zig-zag width. For straight stitching higher quality stitching may be performed if a throat plate with a constricted needle aperture is employed and improved work feeding will result, particularly when stitches are required to be placed close to the edge of a work panel, if at least one limb of the work feed dog is located closely adjacent to the throat plate needle aperture.
This, of course, can be accomplished by exchanging the entire feed dog in the machine but such exchange requires the use of tools, creates the problem of storage of loose parts, and involves the inconvenience of a series of manual operations.
The U.S. Pat. No. 3,320,912, May 23, 1967 of S. J. Ketterer et al discloses a solution to this problem of conversion between zig-zag and straight stitch work feed dog arrangements by providing a feed dog in which one limb is articulated so that it can be shifted quickly to influence the spacing between the feed dog limbs. The increased mass of the feed dog which this patented arrangement requires also increases the inertia forces which develop during operation of the work feed mechanism and the looseness of parts in the feed system gives rise to increased vibration, noise and wear in the feed system.